Lori Berenson with her son at Lima international airport before boarding a plane to the US. Photograph: Frank Bajak/AP

The American activist Lori Berenson, who stirred international controversy after being convicted of helping Peruvian guerrillas, is returning to the US for her first visit since Peruvian authorities arrested her in 1995.

The 42-year-old, who is on parole, boarded a Continental Airlines flight at Lima's main airport under intense media scrutiny.

Berenson's departure capped three days of confusion after Peruvian authorities prevented her from boarding a flight to New York on Friday despite a court approval allowing her to leave. The court has ordered her to return to Peru by 11 January.

Peruvian migration officials finally gave Berenson another document on Monday clearing her to leave the country with her son.

Her father, Mark Berenson, said he was anxious to see her return.

"I'm just glad that they finally resolved the thing," he said.

Lori Berenson admitted helping the Tupac Amaru rebel group rent a safe house where authorities seized a cache of weapons after a shootout with the rebels. She insists she did not know guns were stored there and says she never joined the group.

In 1996, a military court of hooded judges convicted Berenson of treason and sentenced her to life in prison. After US pressure, she was retried by a civilian court.

Her father said his daughter had every intention of returning to Peru.

By law, she must remain in Peru until her full sentence lapses unless the president, Ollanta Humala, decides to commute it.

Peru remains deeply scarred from its 1980-2000 conflict, which claimed about 70,000 lives.

Its gaping inequalities drew the young Berenson to Peru from El Salvador, where she had worked for the country's top rebel commander during negotiations that led to a 1992 peace accord.

Tupac Amaru was a lesser player in Peru's conflict. The group never set off car bombs or engaged in the merciless slaughter of thousands as Shining Path rebels did, but engaged in kidnappings and selective killings.

In the 1980s, it was known for hijacking grocery trucks and distributing food to the poor.

The group most famously raided the Japanese embassy in Peru in 1996 during a party and held 72 hostages for more than four months. A government raid killed all the rebel hostage-takers.